A Modified Loeffler's Blood Serum Medium Useful in the Routine Health Department Examination for Diphtheria and Streptococcus Infections

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Abstract
A blood serum medium is described, which is almost a selective medium for Corynebacterium diphtheriae. It is easy to prepare, being Loeffler''s medium, modified by addition of 4.5% N/l NaOH yielding a final pH of 7.6, and using brom thymol blue as indicator. The possibility of checking the reaction in the final mixture by the pH "colori-metric" method (Medalia, 1920,1922) makes this medium easy to duplicate, and it yields uniform results. In controlled studies the positive findings on the medium are more than 4 times as many as on routine medium. The ease with which this medium grows C. diphtheriae, almost in a selective way, permits examination to be made in a much shorter time, and the positives are more readily discernible. From the standpoint of Health Department Laboratory examination, it has also been of great value because of the ease with which it grows streptococci; in a study of 2297 cultures, where on the routine Loeffler''s medium only 0.5% streptococci were found predominating, on the modified Loeffler''s, 62% were found.